A catheter is a hollow flexible tube that is often fitted at its distal end with a hypodermic needle or a drug delivery balloon to deliver a therapeutic agent to a target site in the body. For such an application, the proximal end of the catheter will accept or be manufactured with a syringe that is capable of holding a therapeutic agent. To deliver the therapeutic agent using such a catheter, the syringe is filled with the therapeutic agent, pressure is applied to the syringe to force the therapeutic agent into the catheter, and the therapeutic agent is ejected from the catheter's distal end to the target site.
Such a method of drug delivery presents several disadvantages. For instance, such a method is highly inefficient as the entire catheter lumen must be filled with the therapeutic agent before even a small amount can be ejected from the catheter into the target site. In addition, because the therapeutic agent is loaded into the catheter through the proximal end and must pass through the entire length of the catheter to reach the target site, an amount of therapeutic agent inevitably remains in the catheter lumen after delivery. This amount is simply disposed of after delivery, which adds to the expense of the drug delivery procedure. Moreover, it is difficult for viscous, semi-solid or gel-like materials to pass through the entire length of these existing catheters. Accordingly, there is a need for an efficient catheter that reduces the amount of undelivered therapeutic agent and that improves the delivery of a viscous therapeutic agent to the target site.